Year Number 2008-01-01 3.3798 2009-01-01 3.9835 2010-01-01 3.8023 2011-01-01 3.6660 2012-01-01 4.1375 2013-01-01 3.7691 2014-01-01 3.0250 2015-01-01 2.9587 2016-01-01 3.0520 2017-01-01 3.2951